42 inch philips plasma HDTV vertical bar on screen

Question

I have a 42 inch philips plasma HDTV. It's about 4 years old. After it's on for about an hour a vertical bar about 9 inches high and 1 inch wide appears in the upper right corner. What do I need to do to fix this problem? I've rebooted the TV and I've tried to move the picture frame right or left to see if it was off center. Neither has produced results.